为什么我不能启动代理服务?绑定0.0.0.0:8000失败:端口已分配

这是我的docker compose代理。yml

version: "3.7"

services:
  app:
    build:
      context: .
    ports:
      - "8000:8000"
    volumes:
      - ./app:/app
      - static_data:/vol/web

    environment:
      - DB_HOST=db
      - DB_NAME=app
      - DB_USER=postgres
      - DB_PASS=supersecretpassword
      - ALLOWED_HOSTS=127.0.0.1

    depends_on:
      - db

  proxy:
    image : proxy:latest    
    depends_on:
      - app
    ports:
      - "8000:8000"
    volumes:    
      - static_data:/vol/static_data


  db:
    image: postgres:10-alpine
    environment:
      - POSTGRES_DB=app
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=supersecretpassword

volumes:
  static_data: 

我在运行命令之前检查了端口

netstat -ltnp | grep ':8000' 

港口也没有被占用。 当我去

docker-compose -f docker-compose-proxy.yml up

我搞错了

ERROR: for 9bac48e03668_recipe-app-api-devops_proxy_1  Cannot start service proxy: driver failed programming external connectivity on endpoint recipe-app-api-devops_proxy_1 (af5860c135cb37026dcac6ce27151cd4e8448eaddc542d50dcd009c0e24c09fa): Bind for 0.0.0.0:8000 failed: port is already allocated

为什么?如何解决这个问题?